Selectable Eccentric Remodeling and/or Ablation of Atherosclerotic Material

ABSTRACT

A catheter and catheter system for eccentric remodeling and/or removal of atherosclerotic material of a blood vessel of a patient include an elongate flexible catheter body with a radially expandable structure. A plurality of electrodes or other electrosurgical energy delivery surfaces can radially engage atherosclerotic material when the structure expands. An atherosclerotic material detector near the distal end of the catheter body may measure circumferential atherosclerotic material distribution, and a power source selectively energizes the electrodes to eccentrically remodel the measured atherosclerotic material.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional patent application which claimspriority from U.S. patent application Ser. No. 10/938,138, filed on Sep.10, 2004, which is a non-provisional patent application which claims thebenefit under 35 USC 119(e) of U.S. Provisional Patent Application No.60/502,515, filed on Sep. 12, 2003, the full disclosures of which areincorporated herein by reference.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH OR DEVELOPMENT

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REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAMLISTING APPENDIX SUBMITTED ON A COMPACT DISK.

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally related to medical devices, systems,and methods. In an exemplary embodiment, the invention providescatheter-based remodeling and/or removal of atherosclerosis plaquebuilt-up in an artery to improve blood flow, often without balloonangioplasty, stenting, and/or dilation. The structures of the inventionallow image-guided eccentric atherosclerotic material remodeling and/orremoval typically using electrosurgical energy, optionally usingelectrosurgical ablation, often in a controlled environment zone withinthe blood vessel, and ideally with a co-located intravascular imagingcapability. Related embodiments have applications in a variety of bodylumens, including urinary, reproductive, gastrointestinal, and pulmonaryobstructive material removal, optionally for removing or decreasingtumors, cysts, polyps, and the like.

Physicians use catheters to gain access to and repair interior tissuesof the body, particularly within the lumens of the body such as bloodvessels. For example, balloon angioplasty and other catheters often areused to open arteries that have been narrowed due to atheroscleroticdisease.

Balloon angioplasty is often effective at opening an occluded bloodvessel, but the trauma associated with balloon dilation can imposesignificant injury, so that the benefits of balloon dilation may belimited in time. Stents are commonly used to extend the beneficialopening of the blood vessel,.

Stenting, in conjunction with balloon dilation, is often the preferredtreatment for atherosclerosis. In stenting, a collapsed metal frameworkis mounted on a balloon catheter which is introduced into the body. Thestent is manipulated into the site of occlusion and expanded in place bythe dilation of the underlying balloon. Stenting has gained widespreadacceptance, and produces generally acceptable results in many cases.Along with treatment of blood vessels (particularly the coronaryarteries), stents can also be used in treating many other tubularobstructions within the body, such as for treatment of reproductive,gastrointestinal, and pulmonary obstructions.

Restenosis or a subsequent narrowing of the body lumen after stentinghas occurred in a significant number of cases. More recently, drugcoated stents (such as Johnson and Johnson's Cypher™ stent, theassociated drug comprising Sirolimus™) have demonstrated a markedlyreduced restenosis rate, and others are developing and commercializingalternative drug eluting stents. In addition, work has also beeninitiated with systemic drug delivery (intravenous or oral) which mayalso improve the procedural angioplasty success rates.

While drug eluting stents appear to offer significant promise fortreatment of atherosclerosis in many patients, there remain many caseswhere stents either cannot be used or present significant disadvantages.Generally, stenting leaves an implant in the body. Such implants canpresent risks, including mechanical fatigue, corrosion, and the like,particularly when removal of the implant is difficult and involvesinvasive surgery. Stenting may have additional disadvantages fortreating diffuse artery disease, for treating bifurcations, for treatingareas of the body susceptible to crush, and for treating arteriessubject to torsion, elongation, and shortening.

A variety of modified restenosis treatments or restenosis-inhibitingocclusion treatment modalities have also been proposed, includingintravascular radiation, cryogenic treatments, ultrasound energy, andthe like, often in combination with balloon angioplasty and/or stenting.While these and different approaches show varying degrees of promise fordecreasing the subsequent degradation in blood flow followingangioplasty and stenting, the trauma initially imposed on the tissues byangioplasty remains problematic.

A number of alternatives to stenting and balloon angioplasty so as toopen stenosed arteries have also been proposed. For example, a widevariety of atherectomy devices and techniques have been disclosed andattempted. Despite the disadvantages and limitations of angioplasty andstenting, atherectomy has not gained the widespread use and successrates of dilation-based approaches. Still further disadvantages ofdilation have come to light. These include the existence of vulnerableplaque, which can rupture and release materials that may causemyocardial infarction or heart attack.

In light of the above, it would be advantageous to provide new devices,systems, and methods for remodeling and/or removal of atheroscleroticmaterial and other occlusions of the lumens of the body, andparticularly from blood vessels. It would further be desirable to enablethe removal of these occlusive materials without having to resort to thetrauma of a dilation, and to allow the opening of blood vessels andother body lumens which are not suitable for stenting.

BRIEF SUMMARY OF THE INVENTION

In a first aspect, the invention provides a catheter system foreccentric remodeling of atherosclerotic material of a blood vessel of apatient. The system comprises an elongate flexible catheter body havinga proximal end and a distal end with an axis therebetween. A radiallyexpandable structure is disposed near the end of the catheter body, anda plurality of energy delivery surfaces are each oriented radially whenthe expandable structure expands. An atherosclerotic material detectoris disposed for circumferential atherosclerotic material detection. Apower source is electrically coupled to the energy delivery surfaces.The power source energizes the energy delivery surfaces so as toeccentrically remodel the detected atherosclerotic material.

The power source will often selectively energize a subset of the energydelivery surfaces so as to effect eccentric remodeling. The catheterbody may have a lumen extending between the proximal and distal ends,and an aspiration connector may be in fluid communication with the lumenat the proximal end of the catheter body. Proximal and distal debrisbarriers may be disposed proximally and distally of the energy deliverysurfaces, respectively, and an aspiration port may be disposed betweenthe proximal and distal barriers for removal of debris duringatherosclerotic material remodeling.

The atherosclerotic material detector may include an intravascularultrasound catheter disposed in the lumen of the catheter body, anintravascular optical coherence tomography catheter disposed in thelumen, an intravascular catheter having an MRI antenna disposed in thelumen, or the like. Alternative detectors may employ any of a variety ofnon-invasive imaging modalities, including external systems making useof X-rays, CT systems, non-invasive MRI or NMR systems, or the like, sothat the detector may not be disposed in the blood vessel. In someembodiments, a brachytherapy catheter or other restenosis inhibitor maybe advanced distally within the lumen.

The radially expandable body may comprise a plurality of flexiblestruts, and the energy delivery surfaces may define a circumferentiallyoriented array, with the energy delivery surfaces often comprisingelectrodes or microwave antennas. Struts of the radially expandablestructure may have perforations disposed therebetween so as to define anexpandable basket. The basket may have proximal and distal portions withintermediate portion disposed therebetween. The array of electrodes maybe supported along the intermediate portion so as to engage adjacentatherosclerotic material when the basket is expanded within the bloodvessel. The electrodes may comprise conductive surfaces of an electrodestructure mounted to a separately formed basket strut. In otherembodiments, electrode surfaces may be formed as part of the expandablestructure. For example, the electrodes may comprise a localized wideningof an associated strut, often disposed near center of a length of thestrut. The expandable structure may comprise Nitinol™, and the remainingsurface of the Nitinol strut may be insulated. For example, the surfacemay be coated with a high temperature polymer (such as a polyimide orthe like). Other coatings may alternatively be used, includingpolyurethane. The struts may be electrically insulated from each other,so that each strut can be used to conduct energy to an electrode surfaceassociated with the strut from a conductor extending proximally from thestrut so as to independently couple each electrode surface to acontroller.

A distal membrane may be deployable within the blood vessel distally ofthe electrode so as to inhibit distal movement of debris. A proximalmembrane may be deployable proximally of the electrode so as to inhibitproximal movement of the debris. The membranes may inhibit bloodinteraction with the remodeling process, for example, during ablation ofthe atherosclerotic material. In other embodiments, power supplied tothe energy delivery surfaces may be limited so as to inhibit debrisgeneration, for example, by denaturing the atherosclerotic material, bymelting of atherosclerotic material inside layers of the artery, byshrinking of atherosclerotic material inside layers of the artery(during treatment and/or in a tissue healing response), and the like. Insome embodiments, the distal membrane may be supported by the distalportion of the basket so as to expand radially therewith. The proximalmembrane may be supported by the proximal portion of the basket so as toexpand radially therewith. At least one of the proximal and distalmembranes may comprise a lumen axially off-set from the basket.

While some embodiments may have a single monopolar electrode or two ormore monopolar or bipolar electrodes, the electrodes may comprise anarray of at least three alternatively selectable electrodes distributedcircumferentially about the axis, often comprising six or moreelectrodes. A controller may couple the power source to the electrodearray so as to selectively energize that eccentric subset of theelectrode array in response to the detected atherosclerotic material. Acontroller may selectively energize a subset of the energy directingsurfaces by directing RF energy and/or microwave energy thereto. Theatherosclerotic material detector may comprise an ultrasound transduceror optical coherence reflectrometer. Along with stand-alone structuresthat are insertable into a lumen of the catheter, these detectors mayalso be integrated into the catheter structure. A display may be coupledto the atherosclerotic material detector to show an image ofcircumferential atherosclerotic material thickness distributed about thecatheter axis.

In another aspect, the invention provides a catheter system foreccentric remodeling and/or removal of atherosclerotic material from ablood vessel of a patient. The system comprises an elongate flexiblecatheter body having a proximal end and a distal end with an axistherebetween. A radially expandable structure is disposed near thedistal end of the catheter body. A plurality of electrodes are orientedto be radially urged against atherosclerotic material when theexpandable structure expands. An atherosclerotic material detector orimaging sensor is disposed near the distal end of the catheter body forcircumferential identification and measurement of atheroscleroticmaterial. A power source is electrically coupled to the electrodes. Thepower source energizes the electrodes so as to eccentrically removeand/or ablate the measured atherosclerotic material.

The catheter body will often have a lumen extending between the proximalend and the distal end. The lumen may be used as an aspiration lumen,for example, using an aspiration source in fluid communication with thelumen at the proximal end of the catheter body. Proximal and distalablation debris barriers may be disposed proximally and distally of theelectrodes, respectively, with an aspiration port disposed between theproximal and distal barriers for removal of ablation debris duringatherosclerotic material ablation. The atherosclerotic material detectormay comprise an ultrasound transducer of an intravascular ultrasoundcatheter, with the intravascular ultrasound catheter disposed in thelumen. Alternatively, other imaging modalities may be employed,including intravascular optical coherence tomography. Imaging oratherosclerotic material detecting capabilities might also beincorporated into the catheter body in some embodiments, withcircumferential atherosclerotic thicknesses often being measured. Anirrigation lumen may extend between the proximal end of the catheterbody and the distal end of the catheter body, facilitating an enhancedlocal ablation environment adjacent the electrodes. A restenosisinhibitor may be advanced within the lumen, the restenosis inhibitoroptionally comprising an intravascular radiation catheter, restenosisinhibiting drugs, or the like.

The radially expandable body may comprise a plurality of flexiblemembers or struts, the electrodes optionally defining a circumferentialelectrode array. The struts may have perforations or openingstherebetween so as to define an expandable basket. The array ofelectrodes may be supported along an intermediate portion of the basketand oriented radially so as to engage adjacent atherosclerotic materialwhen the basket is expanded within a blood vessel. An aspiration port influid communication with an interior of the basket may facilitateremoval of any ablation debris and tissue vaporization gasses, and mayinhibit release of these byproducts of ablation within the blood vessel,and fluid flowing within the basket may act as a cooling fluid to limitcollateral tissue damage. A distal membrane or barrier deployable withinthe blood vessel distally of the electrodes may inhibit distal movementof any ablation debris, while a proximal membrane or membrane deployableproximally of the electrodes may inhibit proximal movement of anyablation debris. Such member(s) may also reduce or inhibit blood flowwithin a localized remodeling and/or ablation environment. The distalmembrane may be supported by the distal portion of the basket so as toexpand radially therewith, and/or the proximal membrane may be supportedby the proximal portion of the basket so as to expand radiallytherewith. Suitable membranes include, for example, one or more balloonsaxially offset from the basket within the blood vessel, or a braidedsuperelastic material such as Nitinol™ dipped in silicone, polyurethane,PTFE, or another elastic material. In some embodiments, the membrane maybe at least in part integrated with the basket.

The electrodes will often comprise an array of at least three, oftencomprising at least six alternatively selectable electrodes distributedcircumferentially about the axis of the catheter body. The arrays ofelectrodes may be axisymmetric, with an eccentric treatment orientationbeing selected without physically rotating the array by selectivelypairing electrodes of the array. A controller couples the power sourceto the electrode array for selectively energizing an eccentric subset ofthe electrode array in response to the measured atheroscleroticmaterial. Exemplary electrodes may comprise stainless steel soldered tocopper wires, with the copper wires insulated from supporting elementsof associated expandable basket elements. Alternative electrodes maycomprise platinum (which also allows the electrode to serve as aradiopaque marker). The electrode/basket assembly may be, for example,coated with a high temperature polymer, such as a polyimide. Anexemplary electrode array includes alternating axially offsetelectrodes, and the controller will often direct RF bipolar powerbetween pairs of the energized subset of electrodes, the pairsoptionally comprising circumferentially offset electrodes, adjacentaxially aligned electrodes, or alternating between axially andcircumferentially offset electrodes. In some embodiments monopolarenergy may be directed to selected electrodes, with the circuit beingcompleted by a patient ground. More generally, each electrode willtypically comprise a metallic body affixed to an adjacent strut of theexpandable structure by a polymer with an associated conductor extendingproximally from the electrode so as to electrically couple the electrodesurface to the controller.

The exemplary atherosclerotic material detector will comprise anultrasound transducer of an intravascular ultrasound catheter, a sensorof an intravascular optical coherence tomography catheter, or the like.A display may be provided to show an image of circumferential scleroticmaterial thickness about the catheter axis, the display and/or imagingcatheter signals optionally comprising indicia of orientation forrotationally registering the selected electrodes to the measurements.Suitable indicia may comprise a “key” or distinguishable image of atleast one expandable member or marker.

In another aspect, the invention provides a catheter for atheroscleroticmaterial removal from the blood vessel of a patient. The cathetercomprises an elongate flexible catheter body having a proximal end and adistal end with an axial aspiration lumen therebetween. A radiallyexpandable basket near the distal end of the catheter body has aproximal portion and a distal portion with an intermediate portiondisposed therebetween. A circumferential electrode array is distributedabout the intermediate portion of the radially expandable basket so asto ablate adjacent atherosclerotic material when the basket expandswithin the blood vessel. An aspiration port provides fluid communicationbetween the aspiration lumen and an interior of the basket. A distalmembrane supported by the distal portion of the basket inhibits distalmovement of ablation debris when the basket is expanded within the bloodvessel. A proximal membrane supported by the proximal portion of thebasket inhibits proximal movement of ablation debris when the basket isexpanded within the blood vessel.

In a first method aspect, the invention provides a method for remodelingeccentric atherosclerotic material of a blood vessel of a patient. Themethod comprises positioning a working end of a catheter within theblood vessel adjacent the atherosclerotic material, the catheterdefining an axis. The catheter is radially expanded so as to engage atleast one energy delivery surface of the catheter against theatherosclerotic material. A circumferential distribution of theatherosclerotic material about the axis of the catheter is determined.Electrosurgical energy is directed from the at least one energy deliverysurface eccentrically relative to the axis of the catheter in responseto the determined atherosclerotic material distribution.

Remodeling of the atherosclerotic material may comprise ablation,removal, shrinkage, melting, denaturing, and/or the like of theatherosclerotic material. For example, relatively low power RF energymay be used to heat the atherosclerotic material until it melts, thematerial optionally being redistributed along the artery wall, insidelayers of the vessel, or the like. Optionally, the atheroscleroticmaterial may comprise a vulnerable plaque. Vulnerable plaques (and/orblood vessels in which vulnerable plaque is a concern) may be treatedusing RF energy to mildly heat the cap and underlying lipid-rich pool ofthe vulnerable plaque to a temperature in a range from about 50 to about60° Celsius. This may be performed so as to generate thickening of thecap, often as an immune response to heating. Such thickening maypotentially result in restenosis, and cap thickening and/or restenosismay be limited by accurate control of the RF energy, the use ofanti-restenotic drugs (such as Rapamycin™ or the like). In addition tovulnerable plaque stabilization, the invention may be employed toeliminate vulnerable plaques, optionally by heating of the lipid-richpool to a temperature of at least around 90° Celsius. Preferably,heating of the blood vessel will be performed so as to limit atemperature of an adventitia or outer layer of the blood vessel to belowabout 63° Celsius so as to inhibit collagen shrinkage and vesselcollapse. In contrast, mild RF energy may be applied to theatherosclerotic material so as to denature the material and result inshrinkage of the material during or after treatment. Shrinkage ofatherosclerotic material may lead to larger open vessel lumens andimproved blood flow.

When remodeling of atherosclerotic plaques comprises ablation ofatherosclerotic materials, any thrombolitic debris generated may berestrained and/or evacuated. Where ablation generates non-thromboliticdebris, or where remodeling is performed so as to inhibit debrisgeneration, debris restraining and evacuation may be unnecessary.

Electrosurgical energy directed by the one or more energy deliverysurfaces will often comprise RF and/or microwave electrical energy. Thecircumferential distribution of atherosclerotic material may bedetermined using intravascular or non-invasive techniques. Theelectrosurgical energy may be directed eccentrically without rotatingthe energy delivery surfaces about the catheter axis by energizing asubset of the electrodes. The subset of electrodes may be selected inresponse to the determined atherosclerotic material distribution.Selected electrodes may be rotationally registered with theatherosclerotic material distribution, for example, with reference toone or more structures of the expandable basket having a distinguishableimage. For example, a strut of the electrode arbitrarily identified aselectrode 1 may have one radiopaque marker or other distinguishableimage, and a strut of an electrode referenced as electrode 2 may havetwo radiopaque markers or two distinguishable image features. This canhelp identify all of the electrodes, since electrode 1 is identifiableand the direction from electrode 1 to electrode 2 indicates acircumferential electrode count direction. A variety of alternativedistinguishable features with integrated or separate circumferentialelectrode count orientation indicators may also be utilized. In someembodiments, registration may be performed automatically with referenceto an electronic signal.

In yet another aspect, the invention provides a method for eccentricatherosclerotic material removal from a blood vessel of a patient. Themethod comprises positioning a working end of the catheter within theblood vessel and adjacent the atherosclerotic material. The catheterdefines the axis. The catheter is radially expanded so as to engage aplurality of electrodes of the catheter against the atheroscleroticmaterial. A circumferential distribution of the atherosclerotic materialis measured about the axis of the catheter. RF energy is directed fromthe electrodes eccentrically relative to the axis of the catheter inresponse to the measured atherosclerotic material distribution.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates diffuse atherosclerotic disease in which asubstantial length of multiple blood vessels has limited effectivediameters.

FIG. 1B illustrates vulnerable plaque within a blood vessel.

FIG. 1C illustrates the sharp bends or tortuosity of some blood vessels.

FIG. 1D illustrates atherosclerotic disease at a bifurcation.

FIG. 1E illustrates a lesion associated with atherosclerotic disease ofthe extremities.

FIG. 1F is an illustration of a stent fracture or corrosion.

FIG. 1G illustrates a dissection within a blood vessel.

FIG. 1H illustrates a circumferential measurement of an artery wallaround a healthy artery.

FIG. 1I illustrates circumferential distribution of atheroma about arestenosed artery.

FIG. 2 schematically illustrates an atherosclerotic material cathetersystem according to the present invention.

FIG. 2A schematically illustrates a catheter system for remodelingatherosclerotic material, the system including the catheter of FIG. 2.

FIG. 3 illustrates an expandable basket and an associated electrodearray of the catheter system of FIG. 2.

FIGS. 4 and 5 illustrate alternative basket structures for use with thecatheter system of FIG. 2.

FIGS. 6A and 6B illustrate an exemplary basket structure havingalternating axially offset electrodes in a circumferential array.

FIGS. 7A and 7B illustrate an exemplary ablation debris barrier for usewith a basket.

FIG. 7C illustrates an alternative basket and debris barrier.

FIG. 8 illustrates electrodes having dedicated conductors mounted toassociated elements of a superelastic metal basket.

FIG. 9 is an illustration of a basket comprising polyimide supporting acircumferential array of electrodes.

FIGS. 10A-E illustrate an exemplary atherosclerotic material remodelingand/or removal method using the catheter system of FIG. 2.

FIGS. 11-21 schematically illustrate alternative catheters and cathetersystems for use in the methods described herein.

FIGS. 22-25 schematically illustrate controllers for selectivelyenergizing electrodes in the system of FIG. 2.

FIGS. 26 and 27 schematically illustrate alternative fluid flow pathsfor use in an atherosclerotic material remodeling catheter.

FIGS. 28A-28D illustrate an alternative controller for selectivelyenergizing electrodes in the system of FIG. 2.

FIGS. 29A-29H illustrate an alternative basket structure formed withindependent struts having a localized enhanced width for use as anelectrode surface, along with components thereof.

FIGS. 30A and 30B schematically illustrate electrical circuitry allowingthermocouples and other temperature sensors to be used both formeasuring temperature and as electrodes.

FIG. 31 schematically illustrates an alternative catheter structure foruse in the methods described herein.

FIGS. 32A-32D schematically illustrate alternative basket and catheterstructures for use in the methods described herein.

FIG. 33 schematically illustrates an alternative catheter structureusing microwave energy to remodel atherosclerotic material.

FIG. 34 schematically illustrates an alternative catheter structurehaving lumens extending toward the electrodes so as to provide directedirrigation flow in the methods described herein.

FIG. 35 schematically illustrates a further alternative catheter basketstructure having lumens for directing irrigation flow toward themicrowave antennas for use in the methods described herein.

FIG. 36 is a schematic cross sectional view showing the application ofdifferent power levels through different electrodes so as toeccentrically remodel atherosclerotic materials.

FIGS. 37A-37C illustrate a further alternative catheter basketstructure, in which the basket comprises polyimide for supporting acircumferential array of electrodes and facilitating intravascularimaging.

FIGS. 38A-38E are cross sectional side views through a body lumenshowing additional aspects of treatment methods and devices describedherein.

FIGS. 38F-38H are cross sectional views taken across a body lumen andtreatment device to show additional aspects of the eccentric treatmentmethods and devices.

FIGS. 39A and 39B illustrate an eccentric treatment device and method ina gelatin artery model.

FIG. 40 is a perspective view of an exemplary catheter assembly.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides devices, systems, and methods to remodela partially occluded artery in order to open the artery lumen andincrease blood flow. Remodeling may involve the application ofelectrosurgical energy, typically in the form of RF and/or microwaveelectrical potentials to energy delivery surfaces such as electrodes,antennas, and the like. This energy will often be controlled so as tolimit a temperature of target and/or collateral tissues, for example,limiting the heating of a fibrous cap of a vulnerable plaque or theintimal layer of an artery structure to a maximum structure in a rangefrom about 50 to about 60° Celsius, by limiting the maximum temperatureof an outer layer or adventitia of the blood vessel to no more thanabout 63° Celsius, limiting heating of a lipid-rich pool of a vulnerableplaque sufficiently to induce melting of the lipid pool while inhibitingheating of other tissues (such as an intimal layer or fibrous cap) toless than a temperature in a range from about 50 to about 60° Celsius soas to inhibit an immune response that might otherwise lead torestenosis, or the like. Relatively mild heating energies may besufficient to denature and shrink atherosclerotic material duringtreatment, immediately after treatment, and/or more than one hour, morethan one day, more than one week, or even more than one month after thetreatment through a healing response of the tissue to the treatment soas to provide a bigger vessel lumen and improved blood flow.

In some embodiments, remodeling of the atherosclerotic plaque maycomprise the use of higher energies to ablate and remove occlusivematerial from within body lumens, and particularly to removeatherosclerotic material from a blood vessel in order to improve bloodflow. Ablation debris may be generated by such ablation, and theablation debris may be thrombolitic or non-thrombolitic. Wherethrombolitic debris is generated by ablation, that debris may berestrained, captured, and/or evacuated from the treatment site.Non-thrombolitic debris produced by ablation may not have to berestrained and/or evacuated from the vessel. The techniques of theinvention will often provide electrosurgical capabilities, sensing orimaging suitable for measuring atheroma and/or vascular walls, and/or anemboli inhibitor. As atherosclerosis may be eccentric relative to anaxis of the blood vessel over 50% of the time, possibly in as much as(or even more than) 75% of cases, the devices and methods of the presentinvention will often be particularly well suited for directing treatmenteccentrically, often in response to circumferential atheroscleroticmaterial detecting or imaging. While the methods and devices describedherein allow such eccentric treatments, the devices can also be used fortreatment of radially symmetric atherosclerosis by selectively directingenergy in a radially symmetric pattern about an axis of the catheter orthe like.

Hence, remodeling of atherosclerotic materials may comprise ablation,removal, shrinkage, melting, and the like of atherosclerotic and otherplaques. Optionally, atherosclerotic material within the layers of anartery may be denatured so as to improve blood flow, so that debris willnot necessarily be generated. Similarly, atherosclerotic materialswithin the arterial layers may be melted and/or treatment may involve ashrinking of atherosclerotic materials within the artery layers, againwithout necessarily generating treatment debris. The invention may alsoprovide particular advantages for treatment of vulnerable plaques orblood vessels in which vulnerable plaque is a concern. Such vulnerableplaques may comprise eccentric lesions, and the present invention may beparticularly well suited for identifying an orientation (as well asaxial location) of the vulnerable plaque structure. The invention willalso find applications for targeting the cap structure for mild heating(to induce thickening of the cap and make the plaque less vulnerable torupture) and/or heating of the lipid-rich pool of the vulnerable plaque(so as to remodel, denature, melt, shrink, and/or redistribute thelipid-rich pool.

While the present invention may be used in combination with stentingand/or balloon dilation, the present invention is particularly wellsuited for increasing the open diameter of blood vessels in whichstenting and balloon angioplasty are not a viable option. Potentialapplications include treatment of diffuse disease, in whichatherosclerosis is spread along a significant length of an artery ratherthan being localized in one area. The invention may also provideadvantages in treatment of vulnerable plaque or blood vessels in whichvulnerable plaque is a concern, both by potentially identifying andavoiding treatment of the vulnerable plaque with selected eccentricand/or axial treatments separated from the vulnerable plaque, and byintentionally ablating and aspirating the cap and lipid-rich pool of thevulnerable plaque within a controlled environmental zone or regionwithin the blood vessel lumen. The invention may also find advantageoususe for treatment of tortuous, sharply-curved vessels, as no stent needbe advanced into or expanded within the sharp bends of many bloodvessel. Still further advantageous applications include treatment alongbifurcations (where side branch blockage may be an issue) and in theperipheral extremities such as the legs, feet, and arms (where crushingand/or stent fracture failure may be problematic).

Diffuse disease and vulnerable plaque are illustrated in FIGS. 1A and1B, respectively. FIG. 1C illustrates vascular tortuosity. FIG. 1Dillustrates atherosclerotic material at a bifurcation, while FIG. 1Eillustrates a lesion which can result from atherosclerotic disease ofthe extremities.

FIG. 1F illustrates a stent structural member fracture which may resultfrom corrosion and/or fatigue. Stents may, for example, be designed fora ten-year implant life. As the population of stent recipients liveslonger, it becomes increasingly likely that at least some of thesestents will remain implanted for times longer than their designed life.As with any metal in a corrosive body environment, material degradationmay occur. As the metal weakens from corrosion, the stent may fracture.As metal stents corrode, they may also generate foreign body reactionand byproducts which may irritate adjoining body tissue. Such scartissue may, for example, result in eventual reclosure or restenosis ofthe artery.

Arterial dissection and restenosis may be understood with reference toFIGS. 1G through 1I. The artery comprises three layers, an endotheliallayer, a medial layer, and an adventitial layer. During angioplasty, theinside layer may delaminate or detach partially from the wall so as toform a dissection as illustrated in FIG. 1G. Such dissections divert andmay obstruct blood flow. As can be understood by comparing FIGS. 1H and1I, angioplasty is a relatively aggressive procedure which may injurethe tissue of the blood vessel. In response to this injury, in responseto the presence of a stent, and/or in the continuing progression of theoriginal atherosclerotic disease, the opened artery may restenose orsubsequently decrease in diameter as illustrated in FIG. 1I. While drugeluting stents have been shown to reduce restenosis, the efficacy ofthese new structures several years after implantation has not be fullystudied, and such drug eluting stents are not applicable in many bloodvessels.

In general, the present invention provides a catheter which isrelatively quick and easy to use by the physician. The catheter systemof the present invention may allow arteries to be opened to at least 85%of their nominal or native artery diameter. In some embodiments,arteries may be opened to about 85%, and/or acute openings may be lessthan 85%. Rapid occlusive material removal may be effected usingsufficient power to heat tissues locally to over about 100° C. so as tovaporize tissues, or more gentle remodeling may be employed.

The desired opening diameters may be achieved immediately aftertreatment by the catheter system in some embodiments. Alternatively, amilder ablation may be implemented, for example, providing to no morethan a 50% native diameter when treatment is complete, but may stillprovide as much as 80 or even 85% or more native vessel open diametersafter a subsequent healing process is complete, due to resorption ofinjured luminal tissues in a manner analogous to left ventricularablation for arrhythmia and transurethral prostate (TURP) treatments.Such embodiments may heat at least some occlusive tissue to atemperature in a range from about 55° C. to about 80° C. In someembodiments, occlusive tissues may be heated to a maximum temperature ina range between about 93 and 95° C. In other embodiments describedherein, heating may be controlled so as to provide tissue temperaturesin a range between about 50 and 60° C., with some embodiments benefitingfrom maximum tissue temperatures of about 63° C. Still furthertreatments may benefit from treatment temperatures of about 90° C.Advantageously, the catheter systems and methods of the invention may beused without balloon angioplasty, thereby avoiding dissections andpotentially limiting restenosis.

An exemplary catheter system 10 is schematically illustrated in FIGS. 2and 2A. A remodeling and/or ablation catheter 12 includes a catheterbody 14 having a proximal end 16 and a distal end 18. Catheter body 14is flexible and defines a catheter axis 20, and includes an aspirationlumen 22 and an irrigation lumen 24 (see FIG. 3). Still further lumensmay be provided for a guidewire, imaging system, or the like asdescribed below. Lumen 22 may be used for sensing and/or imaging ofatheroma as well as aspiration.

Catheter 12 includes a radially expandable structure 26 adjacent distalend 18 and a housing 28 adjacent proximal end 16. A distal tip 30 mayinclude an integral tip valve to seal aspiration lumen 22 and allowpassage of guidewires, imaging and/or restenosis inhibiting catheters,and the like.

Proximal housing 28 includes a first connector 32 in fluid communicationwith aspiration lumen 22. Aspiration lumen 22 may have an aspirationport within expandable structure 26 so as to allow aspiration oraspiration of debris and gasses from within the expandable structure.Aspiration lumen 22 may also be used as an access lumen for guidewires,intravascular imaging catheters, and/or distally advancing intravascularradiation treatment catheters or restenosis inhibiting drugs. Hence,connector 32 may selectively accommodate an imaging catheter 34 havingan atherosclerotic material detector 36 advancable within catheter body14 adjacent to and/or beyond distal end 18, the detector oftencomprising an intravascular ultrasound transducer, an optical coherenttomography sensor, an MRI antenna, or the like. An imaging connector 38of imaging catheter 34 transmits imaging signals allowingcircumferential measurement of atherosclerotic thicknesses about axis 20to a display 39.

Connector 32 also accommodates a restenosis inhibiting treatmentcatheter 40, the treatment catheter here comprising an intravascularradiation catheter. Such a radiation catheter may include a radiationsource 42 which can again be advanced distally within catheter body 14to or beyond expandable structure 26.

A second connector 44 of proximal housing 28 is in fluid communicationwith irrigation lumen 24 (see FIG. 3). Second connector 44 may becoupled to an irrigation fluid source for introducing conductive ornon-conductive liquids, gases, or the like, ideally for introducing gasor heparinized saline. Both first and second connectors 32, 44 mayoptionally comprise a standard connector such as a Luer-Loc™ connector.In FIG. 2A connector 44 is schematically shown coupled to an aspirationvacuum source/infusion fluid source 45.

Referring now to FIGS. 2, 2A, and 3, proximal housing 28 alsoaccommodates an electrical connector 46. Connector 46 includes aplurality of electrical connections, each electrically coupled to anelectrode 50 via a dedicated conductor 52. This allows a subset ofelectrodes 50 to be easily energized, the electrodes often beingenergized with bipolar or monopolar RF energy. Hence, electricalconnector 46 will often be coupled to an RF generator via a controller47, with the controller allowing energy to be selectively directed to aneccentric portion of an engaged luminal wall. When monopolar RF energyis employed, patient ground may (for example) be provided by an externalelectrode or an electrode on catheter body 14. A processor 49 maymanipulate signals from imaging catheter 34 to generate an image ondisplay 39, may coordinate aspiration, irrigation, and/or treatment, andmay automatically register the treatment with the image.

Expandable structure 26 is illustrated in more detail in FIG. 3.Expandable structure 26 may expand resiliently when released from withina restraining sheath, or may expand by pulling tip 30 toward distal end18 (see FIG. 2), optionally using a pullwire, an inner catheter body 58,or the like. Expandable structure 26 here comprises a perforatestructure or basket having a series of structural struts or elements 54with opening or perforations 56 therebetween. Perforations 56 may beformed, for example, by cutting elongate slits in a flexible tubematerial, or the basket may be formed by braiding elongate wires orribbons or the like.

Expandable structure 26 generally includes a proximal portion 60, adistal portion 62, and an intermediate portion 64 therebetween. Eachelectrode 50 is mounted on an associated basket element 54 alongintermediate portion 64, with an associated conductor 52 extendingproximally from the electrode. Electrodes 50 are distributedcircumferentially about axis 20 in an array, adjacent electrodespreferably being axially offset, ideally being staggered or alternatingbetween proximal and distal axial locations. This allows bipolar energyto be directed between adjacent circumferential (axially offset)electrodes between adjacent distal electrodes, between adjacent proximalelectrodes, and the like.

In the exemplary embodiment, proximal and distal barriers 66, 68 expandradially with proximal and distal portions 60, 62 of expandablestructure 26. Barriers 66, 68 inhibit any ablation debris and gasesgenerated adjacent electrodes 50 from traveling within the body lumenbeyond catheter 12. Barriers 66, 68 also allow an at least partiallyisolated ablation environment to be established within the body lumen,for example, by replacing blood within a blood vessel with a moreadvantageous fluid environment for limiting charring of the electrodesand the like. Alternative barriers may be provided instead of (or incombination with) barriers 66, 68, including one or more balloonsaxially offset from expandable member 26, elastic lips as shown in FIG.11-13, or the like. In other embodiments remodeling may be effectedwithout generating significant thermolytic ablation debris and/or adesired treatment environment may be provided with localized irrigationand/or aspiration flows so that some systems may forego the use ofbarriers.

Referring now to FIGS. 4 and 6A, alternative embodiments may usedifferent expandable structures in the form of different baskets. InFIG. 4, a braided basket 70 includes electrodes 50 mounted on braidedstructures 72. While metallic braided structures may be used in someembodiments with attention to electrical isolation of the electrodes,shorting of crossing metallic braided structures may be problematic.Hence, braided members 72 may comprise a high-temperature polymer ornon-conductive material such as polyimide. An elongate electrode basket76 may include electrodes 50 formed, for example, by selectivelyexposing a metallic surface along a central portion of basket member 78,while the remainder of the basket element is electrically isolated usinga high-temperature polymer or the like so that the basket struts may beused as a conductor for energizing the electrode. Radial expansion ofbasket 76 is also illustrated by movement 71 of inner catheter body 58relative to body 14. Expansion may also be effected by withdrawing asleeve from over the basket, a pull wire, or the like. An intravascularultrasound image sensor 36 of imaging catheter 34 is illustrated in FIG.5 distal of expandable structures 76, with a proximal portion of theimaging catheter removed for clarity. Still further alternativeexpandable structures may be employed, including systems in which anarray of electrodes is mounted circumferentially about a balloon, whichmay reduce blood contamination in the ablation area. Alternatively, acontrolled ablation environment may be maintained with barriersproximally and/or distally of the expandable member by axially offsetballoons, with an optional aspiration port again being disposed betweensuch proximal and distal barriers.

An exemplary expandable structure 26 is formed by cutting slots in asuperelastic alloy tube such as a nickel titanium alloy or Nitinol™tube. As can be understood with reference to FIG. 6B, expandablestructures 54 may have circumferential widths 80 which are enhancedadjacent an electrode and/or electrode mounting location 82. As can beseen in FIG. 6A, the localized enhancement of the width 80 adjacentelectrode mounting pads 82 may be axially offset, as described above.The slots forming expandable members 54, and hence the expandablemembers themselves may, for example, be 0.8 inches in length, with theexpandable members having a circumferential width of about 0.25 inches.

Referring now to FIGS. 7A and 7B, side and end views of an expandablebarrier in the form of a collapsible cone can be seen. Barrier 66 herecomprises a braided Nitinol™ wire 84 coated in silicone, for example, bydipping a braid of a superelastic alloy such as a Nitinol™ braid inliquid silicone and allowing it to harden. Such cones may then bemounted over the proximal and distal portions of the expandablestructure. As noted above, a variety of alternative barrier membranesmay be employed. FIG. 7C illustrates a basket 75 with an integralbarrier 77 coated directly on the basket. Barrier 77 comprises apolyurethane, which may be quite tear resistant. Alternative barriermembranes may comprise other materials such as PTFE or the like.

Referring now to FIGS. 8 and 9, exemplary electrodes 50 supported bypolyimide alloy expandable members 54 may be coated with ahigh-temperature polymer. Conductors 52 extend proximally fromelectrodes 50 as described above. High contrast radiopaque markers suchas gold, platinum, platinum/iridium alloy, and the like may be attachedto or near these struts. The markers could also be used as theelectrodes.

The use of catheter system 10 for remodeling and/or removal of eccentricatheroma from within a blood vessel can be understood with reference toFIGS. 10A through 10E. As seen in FIG. 10A, accessing of a treatmentsite will often involve advancing a guidewire GW within a blood vessel Vat, and more often distally beyond a target region of atheroscleroticmaterial AM. A wide variety of guidewires may be used. For accessing avessel having a total occlusion, guidewire GW may comprise anycommercially available guidewire suitable for crossing such a totalocclusion, including the Safe-Cross™ RF system guidewire havingforward-looking optical coherence reflectrometry and RF ablation. Whereatherosclerotic material AM does not result in total occlusion of thelumen, such capabilities need not be provided in guidewire GW, althoughother advantageous features may be provided. For example, guidewire GWmay include a distal balloon to hold the guidewire in place and furtherinhibit movement of ablation debris and the like. Guidewire GW may bepositioned under fluoroscopic (or other) imaging.

Catheter 12 is advanced distally over guidewire GW and positionedadjacent to atherosclerotic material AM, often toward a distal portionof the occlusion as can be understood with reference to FIGS. 10A and10B. Expandable structure 26 expands radially within the lumen of theblood vessel so that electrodes 50 radially engage atheroscleroticmaterial AM. Expandable structure 26 may be expanded by, for example,pulling a pullwire extending through catheter body 14 to the coupled(directly or indirectly) to distal portion 62 of expandable body 26 (seeFIG. 3). Alternatively, an inner catheter body 58 may be movedproximally relative to outer catheter body 14, with the inner catheteragain being coupled to the distal portion of the expandable body. Stillfurther alternatives are possible, including withdrawing a sheath fromaround the expandable body and allowing the expandable body to flexradially outwardly. In at least some embodiments, whether actuated fromthe proximal end of catheter 12 or simply by releasing the expandablebody, the structural members defining the expandable body may compriseelastic or superelastic materials treated to expand radially outwardly,such as by heat-setting a superelastic Nitinol™ metal, polyimide, or thelike. In some embodiments, guidewire GW may be removed after theablation catheter is positioned and/or the basket is expanded. Asatherosclerotic material AM is distributed eccentrically about catheter12, some of electrodes 50 directly engage a luminal wall W, as can beunderstood with reference to FIGS. 10B and 10C.

Imaging catheter 34 is positioned within a lumen of catheter 12 so thatdetector 42 extends to adjacent atherosclerotic material AM. The imagingcatheter operates within and/or through catheter 12 so as to measure athickness of atherosclerotic material concentrically about catheter 12as illustrated in FIG. 10C with measurements often being taken at aplurality of axial locations so as to measure axial variation of theatherosclerotic material AM within the blood vessel, such measurementsoften progressing proximally. In many cases, atherosclerotic material AMwill be distributed eccentrically within the vessel wall as shown inFIG. 10C. It should be noted that no portion of the vessel wall need becompletely uncovered by atherosclerotic material for the measurementdistribution to indicate that the obstruction is eccentric, as arelatively thin layer of atheroma along one portion or side of the bloodvessel may be much different in thickness than a very thick layer ofatherosclerotic material on an opposite side of the blood vessel V. Insome methods, remodeling and/or ablation of all atheroma along one sidemay result in electrode/vessel wall engagement only after treatmentbegins.

In some cases, imaging catheter 34 may allow identification and/orcharacterization of atherosclerotic materials, plaques, tissues,lesions, and the like from within a blood vessel. For example, imagingcatheter 34 may determine an axial and/or circumferential localizationof a target plaque for treatment. Where treatments are intended foratherosclerotic plaques so as to enhance blood flow through the lumen,the treatment may be tailored to provide short term and/or long termincreases in lumen diameter and blood flow. Where catheter 34 identifiesa circumferentially and/or axially localized vulnerable plaque, thatvulnerable plaque may be targeted for a suitable treatment to inhibitdeleterious release of thrombolitic materials, often by thickening afibrous cap of the vulnerable plaque, making the plaque less vulnerableto rupture, decreasing a size or danger of release from a lipid-richpool of the vulnerable plaque, or the like. Hence, catheter 34 may beused to provide information similar to that available through histologyso as to indicate a composition of an atheroma (by identifying andlocation, for example, a fibrous cap, smooth muscle cells, a lipid pool,calcifications, and the like.) Intravascular ultrasound catheters maynow be capable of such atheroma characterizations, and thesecharacterizations may also be provided by optical coherence tomographyintravascular catheters, intravascular MRI antennas, and othercatheter-based imaging systems, or by non-invasive imaging modalitiessuch as MRI systems, and the like.

Suitable imaging catheters for use in the present catheter system arecommercially available from a wide variety of manufacturers. Suitabletechnology and/or catheters may, for example, be commercially availablefrom SciMed Life Systems and Jomed-Volcano Therapeutics (providers ofintravascular ultrasound catheters), Light Lab™ Imaging (developing andcommercializing optical coherence tomography catheters for intravascularimaging), Medtronic CardioRhythm, and the like. Still furtheralternative technologies may be used, including ultra fast magneticresonance imaging (MRI), electrical impedance atheroma depthmeasurements, optical coherence reflectrometry, and the like.

The systems, devices, and methods described herein may optionally makeuse of imaging techniques and/or atherosclerotic material detectordevices which are at least in part (optionally being entirely) disposedoutside of the body lumen, optionally being disposed outside of thepatient body. Non-invasive imaging modalities which may be employedinclude X-ray or fluoroscopy systems, MRI systems, external ultrasoundtransducers, and the like. Optionally, external and/or intravascularatherosclerotic material detectors may also be used to providetemperature information. For example, a system having an MRI antenna maydetect tissue temperatures such that a graphical indication of treatmentpenetration may be presented on the system display. Tissue temperatureinformation may also be available from ultrasound and/or opticalcoherence tomography systems, and the temperature information may beused as feedback for directing ongoing treatments, for selecting tissuesfor treatment (for example, by identifying a hot or vulnerable plaque),and the like.

As with positioning of guidewire GW and advancement of catheter 12,positioning of sensor 30 of imaging catheter 34 may be facilitated byfluoroscopic or other imaging modalities. Location of sensor 36 relativeto expandable structure 26 may be facilitated by radiopaque markers ofcatheter 34 adjacent sensor 36, and by the radiopaque structure (orcorresponding radiopaque markers placed on or near) expandable structure26, and/or by the use of radiopaque electrodes.

By expanding expandable structure 26 within blood vessel V, optionalproximal and distal barriers 66, 68 (see FIG. 3) may form an at leastpartially, and preferably a substantially isolated environment withinthe blood vessel. That environment may be adapted to improve subsequentremodeling and/or ablation by aspirating blood from a port of aspirationlumen 22 disposed between proximal and distal barriers 66, 68, and byirrigating the isolated environment with a desired fluid, as describedabove. When provided, aspiration and/or irrigation may be performed,optionally simultaneously, so as to generate a flow within thecontrolled environment for removal of any vaporization gases, ablationdebris, and the like.

Referring now to FIGS. 10C and 10D, circumferential imaging oftenindicates that remodeling and/or ablation should be targeted to aneccentric portion or region R of the vessel wall W. To aid inregistering the electrodes with the circumferential atheromadistribution, one strut of expandable structure 26 has an identifiableimage, allowing the strut to serve as a rotational alignment key.Registering the electrodes may be achieved using intravascular imagingsuch as intravascular ultrasound (IVUS), optical coherence tomography(“OCT”), intravascular MRI, and/or the like, optionally using externalimaging such as fluoroscopy, magnetic resonance imaging (“MRI”), or thelike. Electronic registration may also be used. In response to thisinformation, RF energy is directed to electrodes within region R. Theseactively energized electrodes define a subset of the overall array ofelectrodes, and selection of this subset of electrodes may beimplemented using a controller as described hereinbelow.

The mechanisms of ablating atherosclerotic material within a bloodvessel have been well described, including by Slager et al. in anarticle entitled, “Vaporization of Atherosclerotic Plaque by SparkErosion” in J. of Amer. Cardiol. (June, 1985), on pp. 1382-6; and byStephen M. Fry in “Thermal and Disruptive Angioplasty: a Physician'sGuide;” Strategic Business Development, Inc., (1990) the fulldisclosures of which are incorporated herein by reference. Suitablevaporization methods and devices for adaptation and/or use in thepresent system may also be described in U.S. Pat. Nos. 5,098,431;5,749,914; 5,454,809; 4,682,596; and 6,582,423, among other references.The full disclosure of each of these references is incorporated hereinby reference.

As illustrated in FIG. 10, energizing of selected electrodes 50 mayresult in vaporization of atherosclerotic material AM, so that theatherosclerotic material is removed from the blood vessel with anaspiration flow F through a lumen of catheter 12. A concurrentirrigation flow helps maintain the environment between the proximal anddistal barriers of the catheter, and these two flows allow gases G andablation debris to be entrained while inhibiting release of such emboliwithin blood vessel V. The fluid may also act as a cooling fluid tolimit heating and collateral damage to other tissues, the circulatingfluid often being at least less than body temperature, optionally beingat or below room temperature.

Referring now to FIG. 10E, as described above, it may not be necessaryto completely remove all atheroma or atherosclerotic material fromwithin the blood vessel. Providing an open lumen having an effectivediameter of at least 80 or 85% of a nominal native lumen diameter may besufficient. Remodeling treatments may provide acute effective opendiameters in a range from about 30% to about 50%. In some embodiments,injury caused to the atherosclerotic material with the energizedelectrodes or other energy directing surfaces may result in subsequentresorption of the injured tissue lesions so as to provide furtheropening of the vessel after termination of treatment as part of thehealing process.

To promote long term efficacy and inhibit restenosis of a treated regionof blood vessel V, a restenosis inhibiting catheter 40 may be advancedthrough a lumen of catheter 12, so that a radiation source 42 irradiatesthe treated region of the blood vessel. Suitable intravascular radiationcatheters are commercially available from Novoste™, Guidant, Johnson &Johnson, and the like. Restenosis inhibiting drugs similar to those nowbeing employed on drug eluting stents may also be advanced through alumen of catheter 12, optionally while the proximal and distal barriersagain help to maintain a controlled environmental zone within the bloodvessel, so that systemic drug delivery might be limited or avoided. Inaddition to known restenosis inhibiting drugs used on drug elutingstents, drugs which cause vasodilation might be employed. Knownrestenosis inhibiting drugs such as Rapamycin™ may also be used.

In some embodiments, expandable structure 26 may remain expanded againstthe vessel wall W and/or atherosclerotic material AM while catheter 12moves within the blood vessel, the catheter often being drawn proximallyduring or between ablation treatments. Analogous movement of a radiallyexpanded perforate basket is employed, for example, when measuringtemperatures of blood vessels so as to detect vulnerable plaque insystems now being developed and/or commercialized by VolcanoTherapeutics. Alternatively, the basket may be repeatedly contracted,axial movement of the catheter 12 employed to reposition the basket,with subsequent expansion of the basket at each of a plurality oftreatment locations along atherosclerotic material AM. Repeatedintravascular imaging or other atherosclerotic material thicknessmeasurements circumferentially about catheter 12 may be employed, withthe remodeling and/or ablation often being halted temporarily so as toallow an image to be acquired intermittently during an ablationprocedure. A final image may be taken to verify remodeling and/orablation has been successful.

Referring now to FIGS. 11 through 21, a variety of alternative catheterstructures are schematically illustrated, with many of these structuresproviding a microenvironment or controlled environmental zone within theblood vessel which has been enhanced for remodeling and/or ablation. Avariety of emboli inhibiting barriers are also described and/orillustrated, including silastic balloons, flexible lips, or expandablecones which may be axially offset from the ablation electrodes. Forexample, referring to FIGS. 11 and 12, a system similar to thatillustrated in FIG. 2 may employ a remodeling and/or ablation sleeve 102having a proximal hub 104 and receiving an imaging catheter and aguidewire GW in an axial lumen of the sheath. A microenvironment isprovided by a microchamber lip 106, which may comprise silicon or thelike. Bipolar electrodes 50 may (though need not necessarily) generategas and/or other ablation debris, which the silicon lip may help tocontain. A vacuum port 108 of hub 104 is in fluid communication with avacuum port 110, while a saline fluid infusion port 112 together with asaline injection passage 114 may be used to control and/or modify themicroenvironment for remodeling and/or ablation. As illustrated in FIG.13, alternate microchambers may be effected using silicon-like lips 116fully encircling the catheter sheath 102, dual balloons, or the like. Asillustrated in FIG. 14, such structures may be combined with a basket118 supporting RF electrodes so as to provide electrode contact within amicrochamber. The basket may optionally comprise a Nitinol™ shapedmemory alloy.

Referring now to FIG. 15, more generally, remodeling/ablation sleeve 102may support electrode 50 for radiofrequency energy, and may provide oneor more lumens for coaxial and/or biaxial insertion of an imagingcatheter 34 (such as an IVUS catheter) and/or guidewire GW. Imagingcatheter 34 may have a transducer in the form of an array 120.

Referring now to FIG. 16, a remodeling/ablation sleeve 102 similar tothat shown in FIGS. 11 and 12 has (here in cross section) has anelectrode wire lumen 122, a saline injection lumen 124, and the openingof the vacuum port 110 to the working lumen of sheath 102 in which theimaging or IVUS catheter 34 and guidewire GW are disposed. A silicon lipor valve 126 allows a vacuum to be transferred to the microenvironment.

Still further alternative arrangements are illustrated in FIGS. 17 and17A. In the embodiment of FIG. 17, an inner electrode 128 is used in abipolar system along with outer electrodes 50, which contact the tissuefor treatment. FIG. 17A schematically illustrates use of a ballooncatheter 130 having a balloon 132 (such as a latex balloon). On thesurface of the latex balloon electrodes 50 are mounted for use inselected pairs. Hence, a balloon (rather than a basket structure) may beused as a radially expandable structure for carrying the electrodes orother energy delivery surfaces.

FIG. 18 schematically illustrates an expandable basket 134 beingcontracted from a large configuration to a small configuration. Thebasket may optionally be used as a cutting basket by providingappropriate edges, and/or may capture emboli within. FIG. 19 illustratesa remodeling/ablation sleeve 102 in which imaging catheter 34 travelsaxially back and forth to image, and in which a silastic balloon 135 isdisposed distal of the treatment debris for emboli capture. FIG. 20illustrates an alternate electrode delivery balloon 138 similar toballoon 132 of FIG. 17A, and illustrates electrodes 50 having flexiblelumen extensions extending proximally therefrom. FIG. 21 schematicallyillustrates an RF electrode within a microchamber provided by proximaland distal barriers 140, 142 of sheath 102, in which a position ofelectrode 50 is actuated in the microchamber.

Referring now to FIGS. 22 and 23, alternative controllers 92 a, 92 bselectively energize electrodes of catheter 12 with RF power suppliedfrom an RF generator 94. A wide range of RF energy types may beemployed, including burst of 500 Khz, different types of waveforms, andthe like. In controller 92 a, a simple dial 96 is turned to point to adesired electrode pair to be energized. A “key” electrode may beregistered with the intravascular imaging system, either electronicallyor by providing an electrode, electrode support member, or attachedmarker which presents a distinct image on the intravascular imagingdisplay. This simplifies selection of one or more eccentric electrodepair along atheroma. Advantageously, catheter 12 need not be rotatedinto a proper orientation to accurately remodel and/or ablate thedesired eccentric atherosclerotic material. Controller 92 b includessimilar capabilities, but allows the operator to select multipleelectrodes for driving bipolar RF energy therebetween, providing greaterflexibility in allowing multiple electrodes to be simultaneouslyenergized. FIGS. 23 and 24 illustrate monopoly control arrangementssimilar to those of FIGS. 21 and 22, respectively. Patient grounding maybe effected by a patient grounding plate, a ring electrode 2 to 5 cmproximal to basket 26, or the like. Once again, no catheter rotation isrequired to orient an active side of the catheter adjacent to thetargeted atheroma since various eccentric ablation orientations can beselected through the electrode selection controller.

FIGS. 26 and 27 schematically illustrate alternative fluid flowarrangements for use in the catheters and methods described herein. Inthe embodiment of FIG. 26, a tubular body 150 extending proximally fromexpandable body 26 includes one or more irrigation ports 152, theirrigation ports here being disposed proximally of the expandable body.An aspiration port 154 contains a tubular body defining a guidewireand/or imaging catheter lumen 156. Irrigation fluid may flow distally,which may also be the direction of blood flow in the body lumen.Irrigation fluid may be aspirated through the aspiration port. In theembodiment of FIG. 27, lumen 154 is used for aspiration and for aguidewire and/or imaging catheter.

An alternative controller is illustrated in FIGS. 28A-D. This controllerallows an operator to choose, for each electrode, whether to keep thatelectrode inactive, electrically couple that electrode to a first pole(sometimes referred to as pole A) of an energy source (such as an RFgenerator or the like), or to electrically couple that electrode to asecond pole or pole B of the energy source. This controller allows awide range of energized electrode configurations, includingpseudo-monopolar modes where all electrodes except one are connected toone pole of the energy source (pole A) and one electrode is connected tothe other pole (pole B). As can be understood with reference to FIG.28A, controller 160 allows testing of many electrode configurations forRF remodeling and/or ablation, particularly those involving two or moreelectrodes. A switch panel 162 is shown in more detail in FIG. 28B. Eachelectrode (in this embodiment, up to eight electrodes) is electricallycoupled to a 3-way switch numbered from 1 to 8, a switch disposed in themiddle position indicates the electrode is not coupled to either pole,while a switch pushed toward the plus sign indicates the associatedelectrode is coupled to a red RF connector with the controller.Similarly, a switch pushed toward the minus sign indicates theassociated electrode is electrically coupled to a black RF connector ofthe control box.

As can be understood with reference to 28C, electrodes associates withswitches 3-8 are not coupled to either pole, electrode 1 is connected tothe red RF connector, and electrode 2 is connected to the black RFconnector. Activation of the RF generator will circulate bipolar RFenergy between electrodes 1 and 2. In FIG. 28D, electrodes 5-8 are notenergized, while electrodes 1 and 3 are coupled to the red RF connector.Electrodes 2 and 4 are connected to the black RF connector, so thatactivation of the RF generator will circulate bipolar RF energy betweenelectrodes 1 and 3 and between electrodes 2 and 4.

An exemplary self-expandable basket is illustrated in FIGS. 29A-29H. Ascan be understood from these drawings, electrodes may be fabricated aspart of the struts 172 from which the basket is formed, for example,using a radially outwardly oriented surface of a localized widening 174of each strut disposed in axially central portion of the strut, as canbe seen in FIGS. 29B and 29E. Each arm may be formed from one piece ofmaterial, optionally comprising a Nitinol™ nickel-titanium shaped memoryalloy, with the struts optionally being laser cut from a Nitinol™ tube.The electrode/basket may be, for example, coated with a high temperaturepolymer such as a polyimide. Electrodes 174 may be formed by inhibitingcoating or removing coating from the desired portion of the associatedstrut 172 (as illustrated in FIG. 29E) so that the electrode surface isexposed for contact with atherosclerotic material. The struts may beseparated from each other and structurally supported with an insulatedmaterial such as ultraviolet (“UV”) cure or heat shrink sleeve, apolyethylene, Nylon™, or the like to form basket 170.

Each strut 172 may be used to conduct energy between electrode surface174 and an electrical conductor extending proximally from the struttoward a controller. Proximal pads for connecting such conductors areillustrated in FIG. 29C, while distal structural pads 178 areillustrated in FIG. 29D. Adjacent electrodes 174 may be axially offsetor staggered as can be seen in FIG. 29F. Insulating coating along eachstrut 172 may be inhibited or removed from an inner surface of proximalpads 176 so as to facilitate connecting of an associated conductivewire, such as by spot welding or the like. Alternative insulatingmaterials may also be used, including parylene coatings, whilealternative methods for attaching struts 172 to a catheter body may beemployed, including adhesive bonding using insulating UV cure, embeddingthe pad structures in polyethylene, and the like.

Exemplary structures for fixing struts 172 of basket 170 to a catheterbody 180 are illustrated in FIG. 29G.

Referring now to FIGS. 29F and 29H, an alternative indicia providing adistinguishable image for rotationally registering selected electrodes174 of basket 170 to images or other atherosclerotic materialmeasurements can be understood. In this embodiment, an electrode 174 ireferenced as electrode 1 may have a radiopaque marker 182 disposed onthe associated strut 172 i. A strut 172 ii supporting an associatedsecond electrode 174 ii may have two radiopaque markers 182 provide acircumferentially asymmetric count indicator allowing all electrodes tobe referenced without ambiguity. The shape of electrodes 50 may vary,for example, electrodes 174 may be wider than other portions of struts172 as illustrated in FIGS. 29A-G.

As described above, remodeling will often be performed using irrigationand/or aspiration flows. In many embodiments, an irrigation port directsfluid, such as a saline solution, from an irrigation lumen to aninterior of the basket. An aspiration port may provide fluidcommunication between an aspiration lumen and an interior of the basket.One or both of these fluid flows may be driven continuously, or mayalternatively pulsate before, during, and/or after treatment. In someembodiments, aspiration and/or irrigation flow may occur acutely orconcurrently so as to circulate between the irrigation port and theaspiration port. Optionally, the flow may carry ablation debris to theaspiration port, where the debris may be evacuated through theaspiration lumen. There may be coordination between the irrigationsystem and the aspiration system such that the irrigation fluid mayremain confined in an area closely adjacent the basket so as to inhibitembolization of ablation debris when the basket is expanded within theblood vessel. Such coordination, for example, may inhibit distalmovement of ablation debris, and/or may obviate any need for a distaland/or proximal barrier or membrane. In some embodiments, thecirculation of fluid between an irrigation port and an aspiration portmay create an effectively bloodless environment adjacent the electrodesto facilitate remodeling and/or ablation, imaging of atherosclerotictissue, and the like.

Referring now to FIGS. 30A and 30B, control of energy directed from thecatheter systems and structures of the present invention may optionallymake use of thermocouples and other temperature sensing structures.Thermocouples such as K-type thermocouples (+CH/−AL) may be attached toor near one or more struts of an expandable structure to providetemperature measurements. For example, such structures may providetissue temperature measurements, blood temperature measurements,treatment temperature measurements, and/or the like.

Optionally, a temperature measurement structure may also be used as anRF electrode, for example, by employing one or more of the structuresillustrated in FIGS. 30A and 30B. In the embodiment of FIG. 30A, athermocouple 182 can be coupled to either an RF energy source 184 or athermometer 186 by a switch 188. A similar embodiment is illustrated inFIG. 30B.

Referring now to FIG. 31, an alternative catheter system 190 includes aplurality of electrodes 50 supported by struts 192. Struts 192 expandradially when extended distally through a sheath 194 so that acircumferential array of the electrodes is collapsible. A ball-shapedtip 196 includes proximally oriented high pressure jets 198, and theball-shaped tip may be used as one pole with selected electrodes 50being used as the other pole. Alternatively, bipolar power may be drivenbetween electrodes 50 or the like. Optionally, a proximal barrier 200such as a screen may be used to inhibit movement and/or capture anydebris.

When the RF electrodes are energized, the high pressure jets may also beactivated so as to provide a saline flush. A venturi effect may entrainthe debris for transport proximally through a catheter lumen forevacuation, typically using an aspiration source coupled to sheath 194.Debris may be trapped in barrier 200 which may comprise a screen, asolid sheet, a net, or the like. In some embodiments, low pressure jetsmay be used from adjacent ball tip 196 in place of high pressure jets.

Referring now to FIGS. 32A-32D, alternative expandable structures mayavoid kinking or flattening of the expandable structure when theexpandable structure bends axially, such as when it is expanded along abend in a body lumen. In the embodiment of FIG. 32C, a coil or helicalexpandable structure 202 has a small profile configuration 204 and alarge profile configuration 206, and may be deployed and/or retracted bytwisting a distal end 208 and/or a proximal tubular body 210 relative toeach other, by a pull/release mechanism, or the like. Aspiration and/orirrigation may be provided through the proximal tubular member 210 asdescribed above, and the coil structure may include a single loop or aplurality of loops so as to provide one or more circumferential rows ofelectrodes 50 when in the expanded configuration 206. In the embodimentof FIG. 32D, an inflatable expandable structure 212 includes axialstruts and/or rings formed as tubular inflatable balloons so as to allowthe expandable structure to expand from the small profile configurationto the shown large-profile configuration.

Still further alternative expandable structures and energy deliverysurfaces are schematically illustrate in FIGS. 33-35. In a microwavetreatment device 216 illustrated in FIG. 33, each strut of a basket mayinclude a helicoidal microwave antenna, with an inner side of theantenna shielded to avoid emitting energy toward the catheter axis.Alternative microwave antennas may also be employed, includingunidirectional antennas which allow depth between an energy deliverysurface and a target tissue to be varied by varying a focus of theantenna. Such focused microwave devices may include antennas that arerotatable about the catheter axis, axially moveable, and the like.

In the embodiments of FIGS. 34 and 35, catheter bodies again support aseries of struts 218, 220 and also have a plurality of irrigation orflush lumens. The irrigation lumens within the catheter body are influid communication with tubular structures extending along the (and insome cases being integrated into the) struts, so that fluid flush ports222 direct saline or other fluids towards electrodes 50 or microwaveantennas 224. Electrosurgical power for the energy delivery surfaces maybe transmitted using the strut structure, or wires 226 may extend alongthe strut to the energy delivery surfaces. In the embodiment of FIG. 35,shield 228 along an inner portion of a microwave antenna 224 can beseen, which may limit microwave energy directed toward an imagingcatheter. For embodiments employing microwave antennas as energydelivery devices, only one antenna of the circumferential array may beenergized at a time, so as to avoid interference between conductorsalong the catheter body.

Referring now to FIG. 36, controllers of the catheter systems describedherein may allow distribution of differing power levels to differingpairs of electrodes. For example, in response to a circumferentialdistribution of atherosclerotic material AM such as that illustrated inFIG. 36, a controller may direct 50 watts of energy to a first electrode230, 30 watts of energy to a pair of second electrodes 232 and only 10watts of energy to a pair of third electrodes 234. Other electrodes mayhave no energy directed thereto, as described above. In someembodiments, a differing power directed to the differing electrodes maybe provided by controlling the duty cycle, for example, with 50 wattsbeing provided by energizing one or more electrode for 50% of the time,30 watts being provided by energizing an electrode 30% of the time, andthe like.

Referring now to FIGS. 37A-37C, many imaging modalities (includingintravascular ultrasound, optical coherence tomography, intravascularMRI, and the like) may be at least in part blocked or degraded bypositioning the image detecting structure within a metallic structuresuch as a basket formed of Nitinol™. Hence, there may be advantages inproducing alternative expandable structures such as baskets comprisingplastics or a polymer. In light of the heat generated by the electrodesof the systems described herein, it may be advantageous for such polymerbasket structures 240 to comprise a high temperature polymer such as apolyimide. Alternative basket structures may comprise HDPE, PET, Nylon™,PEBAX™, and the like. As illustrated in FIG. 37B, proximal ends of thebasket struts may be glued to a shaft 242 at a bond 244. An imagingcatheter guide 246 may extend through a distal end of the basketstructure 248, with the distal end of the basket free to slide axiallyalong the guide. Pullwires 250 may be affixed to the distal end 248, sothat pulling of the pullwires radially expands basket 240, with thepullwires running inside the proximal shaft 242. The basket may beretracted back to its small profile configuration by pushing of thepullwires, or the basket may include biasing means urging the basket tothe small profile configuration. So as to avoid degradation to imagingperformance, polymer tension members similar to fishing line may be usedas pullwires. In the exemplary embodiment, the pole wires compriseNitinol™ which has sufficient compressional rigidity to push the basketto its small profile configuration.

Basket 240 may be formed by cutting struts from a tube of the polymermaterial, with the distal portion 248 preferably remaining uncut. Theproximal ends of the struts may be separated prior to forming bond 244,and ring-shaped RF electrodes may be slid along each arm and glued tothe desired configuration along the intermediate portion of the basket.

Exemplary treatment methods are illustrated in FIGS. 38A-38H. In FIG.38A, the catheter system 260 includes a basket covering sheath 262 overan atherosclerotic material detecting and treating catheter 264 asdescribed above. In this embodiment, outer basket sheath 262 radiallyrestrains the basket 266, which is biased to expand radially whenreleased from the outer sheath, as illustrated in FIG. 38B. In someembodiments, the basket may be expanded after the outer sleeve isretracted, such as by pulling pullwires, rotating one portion of thecatheter relative to the other, or the like. Regardless, as the basketexpands within the vessel V, electrodes 50 of the basket engage thesurrounding vessel wall. An imaging transducer near basket 266 of animaging catheter disposed in a lumen of the treatment catheter evaluatesthe vessel V, and the detection/treatment catheter system 264 is pulledproximally along the artery or vessel V.

When the imaging catheter detects atherosclerotic material AM asillustrated in FIG. 38C, an appropriate subset (possibly including onlya single electrode 50) is activated to remodel the atheroscleroticmaterial AM, as illustrated in FIG. 38D, and the open vessel lumen sizeincreases moderately during treatment. The catheter is pulled proximallyto the next atheroma, which is again detected and treated. A crosssection of the limited open lumen prior to treatment is schematicallyillustrated in FIG. 38F, which also illustrates a saline flush orirrigation lumen 268 of the catheter 264. Treatment energy and themoderate increase in the open lumen diameter of the vessel V areschematically illustrated in the cross section of FIG. 38G. After ahealing response gradually increases the open lumen diameter, the longerterm open lumen results schematically illustrated in FIG. 38H may thenbe provided.

Referring now to FIGS. 38A and B, eccentric material removal in agelatin artery model 270 are presented. Prior to the test, the arterymodel includes a consistent lumen 272 as seen in FIG. 38A. A testeccentric treatment catheter 274 having an expandable basket supportinga circumferential array of electrodes is introduced into lumen 272, withthe expandable basket supporting the electrodes in engagement with theluminal wall. Selected electrodes of test catheter 274 were energized soas to eccentrically treat the gelatin artery model 274, therebyeffecting eccentric remodeling of the gelatin model, in this case byremoving an eccentric volume 276 from along one side of lumen 272. Theorientation and amount of the material removed was controlled byselectively energizing electrodes of test catheter 274.

Referring now to FIG. 40, an exemplary catheter system 280 isillustrated. In this embodiment, catheter body 282 includes only asingle lumen, which is large enough to accommodate an imaging cathetertherein and also to be used as an irrigation lumen to bring irrigationfluid to irrigation ports 284. The lumen may decrease in diameterdistally of irrigation ports 284, with the decreased diameter portion286 fittingly receiving the imaging catheter within the lumen thereof soas to direct the irrigation fluid radially outward through the pluralityof irrigation ports. This embodiment may be particularly useful whenremodeling atherosclerotic materials using the methods illustrated inFIGS. 38A-38H, in which mild heating improves vessel size withoutrequiring aspiration.

Catheter body 282 may include a braided shaft in which conductive wires(for example copper wires or beryllium-copper wires) are coated with ahigh temperature and/or high strength insulation material such as alayer of polyimide or the like. The braided wires may be sandwichedbetween layers of materials forming the shaft of catheter body 282. Theshaft may, for example, comprise a plurality of layers of polyethylene,an inner Teflon™ PTFE layer, an outer nylon layer, and the like.

The wires of shaft 282 may be braided so as to inhibit capacitive lossesbetween wires when electrical currents run through them. Capacitivelosses may be decreased when a wire that carries a current from anenergy source to an electrode of the catheter system and a wire thatcarries a current from an electrode back to the energy source are notparallel, but at an angle, ideally being perpendicular. This may beachieved by braiding the wires with appropriate pitch or a number ofpeaks per inch. The basket structure 170 of catheter system 280 may beincluded, with the basket structure being described in more detail withreference to FIGS. 29A-29H. Guide 286 may extend through basket 170 andmay comprise a material transparent to the imaging catheter, optionallycomprising HDPE, PET, or the like.

Still further alternatives are available. For example, another way toemploy RF energy to remodel atherosclerotic material may be to energizea plurality of the adjacent electrodes with differing RF signals so asto employ the adjacent electrodes as a phase-array. A phase array candirect or steer an electromagnetic signal in a desired direction usingconstructive and destructive interferences between signals of adjacentelements of the array. By controlling phases of the adjacent signals, aphase array of electrodes may provide a focused and/or steerable RFsignal.

Along with controlling steering and directionality, adjusting phases ofadjacent RF electrodes may allow focusing of some or most of the RFenergy at a desired depth D inside the atherosclerotic material whileinhibiting RF energy delivery between the electrode surfaces and depth Dusing constructive and destructive interference between the signals. Forexample, such a system may be employed to preserve the cap of a plaqueso as to reduce restenosis. Inhibiting heating of the cap while focusingenergy toward an internal portion of the plaque may lower an immuneresponse to heat that could otherwise lead to restenosis. Hence,inhibiting heating of the cap may reduce restenosis.

In general, the present invention may use of highly elastic, expandablestructures, particularly of expandable structures formed from structuralmembers separated by perforations so as to define a “basket.” Suchstructures can conform to an artery diameter before, during, and/orafter atherosclerotic material removal. This expandability allows fordirect contact of the electrodes against atheroma, although the systemsof the present invention may also make use of conductive fluidenvironments to complete an RF energy path, or conversely, usenon-conductive fluid to enhance energy directed through tissue. Multipleelectrodes can be distributed circumferentially around an intermediateportion of the expandable structure, and a subset of these electrodescan be activated to allow for eccentric tissue remodeling and/orablation.

Atheroma may be identified and targeted by intravascular imaging, andthese capabilities may be integrated into the remodeling and/or ablationcatheter. Preferably, the intravascular imaging capabilities will bedeployed in a separate catheter which can be advanced within, andremoved from the ablation catheter. In general, this intravascularimaging capability allows the progress of the therapy to be monitored sothat wall perforation can be avoided, while ideally reducing occlusionto no more than 15% of the overall native vessel diameter (either uponcompletion of the treatment or after subsequent tissue healing). Theablation catheter may further allow the use of localized radiation ordrug delivery for antirestenosis treatments. The ablation catheter mayinclude a relatively large lumen allowing selective use of anintravascular imaging system, a radiation delivery or other treatmentcatheter, an aspiration of debris and vaporization gases, with theseuses often being employed sequentially. A guidewire may make use of thisor a separate lumen, and the guidewire may be removed to allow accessfor the restenosis and/or imaging catheters.

While the exemplary embodiments have been described in some detail, byway of example and for clarity of understanding, those of skill in theart will recognize that a variety of modification, adaptations, andchanges may be employed. Hence, the scope of the present inventionshould be limited solely by the appending claims.

1. A catheter system for eccentric removal of atherosclerotic materialfrom a blood vessel of a patient, the system comprising: an elongateflexible catheter body having a proximal end and a distal end with anaxis therebetween; a radially expandable structure near the distal endof the catheter body; a plurality of electrodes oriented to be urgedradially against atherosclerotic material when the expandable structureexpands; an atherosclerotic material detector disposed near the distalend of the catheter body for circumferential measurement ofatherosclerotic material; and a power source electrically coupled to theelectrodes, the power source energizing the electrodes so as toeccentrically ablate the measured atherosclerotic material.
 2. Thecatheter system of claim 1, wherein the catheter body has a lumenextending between the proximal end and the distal end.
 3. The cathetersystem of claim 2, further comprising an aspiration connector in fluidcommunication with the lumen at the proximal end of the catheter body.4. The catheter system of claim 3, further comprising proximal anddistal ablation debris barriers disposed proximally and distally of theelectrodes, respectively, and an aspiration port disposed between theproximal and distal barriers for removal of ablation debris duringatherosclerotic material ablation.
 5. The catheter system of claim 2,wherein the atherosclerotic material detector comprises an ultrasoundtransducer of an intravascular ultrasound catheter, the intravascularultrasound catheter disposed in the lumen.
 6. The catheter system ofclaim 2, further comprising an irrigation lumen extending between theproximal end of the catheter body and the distal end of the catheterbody.
 7. The catheter system of claim 2, further comprising a restenosisinhibitor advancable distally within the lumen so as to inhibitrestenosis of the blood vessel.
 8. The catheter system of claim 7,wherein the restenosis inhibitor comprises a brachytherapy catheterhaving a radiation source.
 9. The catheter system of claim 1, whereinthe radially expandable body comprises a plurality of flexible struts,and wherein the electrodes define a circumferentially oriented electrodearray.
 10. The catheter system of claim 9, wherein struts of theradially expandable structure have perforations disposed therebetween soas to define an expandable basket, wherein the basket has a proximalportion and a distal portion with an intermediate portion disposedtherebetween, an array of electrodes supported along the intermediateportion so as to engage the adjacent atherosclerotic material when thebasket is expanded within the blood vessel, and further comprising anaspiration port in fluid communication with an interior of the basket.11. The catheter system of claim 10, further comprising a distalmembrane deployable within the blood vessel distally of electrodes so asto inhibit distal movement of ablation debris, and a proximal membranedeployable proximally of the electrodes so as to inhibit proximalmovement of the ablation debris, wherein the membranes inhibit bloodinteraction with the ablation process.
 12. The catheter system of claim11, wherein the distal membrane is supported by the distal portion ofthe basket so as to expand radially therewith, and wherein the proximalmembrane is supported by the proximal portion of the basket so as toexpand radially therewith.
 13. The catheter system of claim 12, whereinat least one of the proximal and distal membranes comprises a balloonaxially off-set from the basket.
 14. The catheter system of claim 1,wherein the electrodes comprise an array of at least 6 alternativelyselectable electrodes distributed circumferentially about the axis, anda controller coupling the power source to the electrode array forselectively energizing an eccentric subset of the electrode array inresponse to the measured atherosclerotic material.
 15. The cathetersystem of claim 14, wherein each electrode comprises a metallic bodyaffixed to an adjacent strut of the expandable structure by a polymerwith an associated conductor extending proximally from the electrode soas to electrically couple the electrode surface to the controller. 16.The catheter system of claim 14, wherein the controller selectivelyenergizes electrodes by directing RF energy thereto.
 17. The cathetersystem of claim 1, wherein the atherosclerotic material detectorcomprises an ultrasound transducer or optical coherence reflectrometry.18. The catheter system of claim 2, further comprising a display showingan image of circumferential atherosclerotic material thicknessdistributed about the catheter axis.
 19. A catheter for remodeling ofatherosclerotic material of a blood vessel of a patient, the cathetercomprising: an elongate flexible catheter body having a proximal end anda distal end with lumen therebetween; a radially expandable basket nearthe distal end of the catheter body, the basket having a proximalportion and a distal portion with an intermediate portion disposedtherebetween; and a circumferential electrode array distributedcircumferentially about the intermediate portion of the radiallyexpandable basket so as to selectably remodel adjacent eccentricatherosclerotic material while the basket is expanded within the bloodvessel; an aspiration port providing fluid communication between theaspiration lumen and an interior of the basket.
 20. The catheter ofclaim 19, wherein the catheter body has an aspiration lumen, and furthercomprising: an aspiration port providing fluid communication between theaspiration lumen and an interior of the basket; and a distal membranesupported by the distal portion of the basket so as to inhibit distalmovement of debris when the basket is expanded within the blood vessel,and a proximal membrane supported by the proximal portion of the basketso as to inhibit proximal movement of debris when the basked is expandedwithin the blood vessel.
 21. A catheter for atherosclerotic materialremoval from a blood vessel of a patient, the catheter comprising: anelongate flexible catheter body having a proximal end and a distal endwith an axial aspiration lumen therebetween; a radially expandablebasket near the distal end of the catheter body, the basket having aproximal portion and a distal portion with an intermediate portiondisposed therebetween; a circumferential electrode array distributedcircumferentially about the intermediate portion of the radiallyexpandable basket so as to ablate adjacent atherosclerotic material whenthe basket expands within the blood vessel; an aspiration port providingfluid communication between the aspiration lumen and an interior of thebasket; and a distal membrane supported by the distal portion of thebasket so as to inhibit distal movement of ablation debris when thebasket is expanded within the blood vessel, and a proximal membranesupported by the proximal portion of the basket so as to inhibitproximal movement of ablation debris when the basked is expanded withinthe blood vessel.
 22. A method for remodeling eccentric atheroscleroticmaterial of a blood vessel of a patient, the method comprising:positioning a working end of a catheter within the blood vessel andadjacent the atherosclerotic material, the catheter defining an axisradially expanding the catheter so as to engage at least one energydelivery surface of the catheter against the atherosclerotic material;determining a circumferential distribution of the atheroscleroticmaterial about the axis of the catheter; directing electrosurgicalenergy from the at least one energy delivery surface eccentricallyrelative to the axis of the catheter in response to the determinedatherosclerotic material distribution.
 23. The method of claim 22,wherein the electrosurgical energy is directed eccentrically withoutrotating the energy delivery surfaces about the catheter axis byenergizing a subset of the electrodes, and further comprising selectingthe subset of electrodes in response to the determined atheroscleroticmaterial distribution.
 24. The method of claim 22, further comprisingrotationally registering selected electrodes with the determinedatherosclerotic material distribution.
 25. The method of claim 24,wherein the registration is performed with reference to one or morestructures of the expandable basket having a distinguishable image. 26.The method of claim 24, wherein the registration is performedautomatically with reference to an electronic signal.
 27. A method foreccentric atherosclerotic material removal from a blood vessel of apatient, the method comprising: positioning a working end of a catheterwithin the blood vessel and adjacent the atherosclerotic material, thecatheter defining an axis; radially expanding the catheter so as toengage a plurality of electrodes of the catheter against theatherosclerotic material; measuring a circumferential distribution ofthe atherosclerotic material about the axis of the catheter; directingRF energy from the electrodes eccentrically relative to the axis of thecatheter in response to the measured atherosclerotic materialdistribution.
 28. The method of claim 27, further comprisingrotationally registering selected electrode with the measuredatherosclerotic material distribution.
 29. The method of claim 28,wherein the registration is performed with reference to a asymmetricstructure of the expandable basket having a distinguishable image. 30.The method of claim 28, wherein the registration is performedautomatically with reference to an electronic signal.
 31. A device forremodeling occlusive material of a body lumen of a patient, the devicecomprising: an elongate body having a proximal end and a distal end withan axial aspiration lumen therebetween; a radially expandable basketnear the distal end of the body, the basket having a proximal portionand a distal portion with an intermediate portion disposed therebetween;a circumferential electrode array distributed circumferentially aboutthe intermediate portion of the radially expandable basket so as toremodel adjacent occlusive material when the basket expands within thebody lumen; an aspiration port providing fluid communication between theaspiration lumen and an interior of the basket; and a distal membranesupported by the distal portion of the basket so as so expand themembrane when the basket is expanded within the body lumen, and aproximal membrane supported by the proximal portion of the basket so asto expand the membrane when the basket is expanded within the bodylumen.
 32. A system for eccentric removal of material from a body lumenof a patient, the system comprising: an elongate body having a proximalend and a distal end with an axis therebetween; a radially expandablestructure near the distal end of the catheter body; a plurality ofelectrodes oriented to be urged radially against the material when theexpandable structure expands within the body lumen; a material detectordisposed near the distal end of the catheter body for circumferentialmeasurement of the material; and a power source electrically coupled tothe electrodes, the power source energizing the electrodes so as toeccentrically ablate the measured material.
 33. A device for occlusivematerial removal from a body lumen of a patient, the device comprising:an elongate body having a proximal end and a distal end with an axialaspiration lumen therebetween; a radially expandable basket near thedistal end of the body, the basket having a proximal portion and adistal portion with an intermediate portion disposed therebetween; acircumferential electrode array distributed circumferentially about theintermediate portion of the radially expandable basket so as to ablateadjacent occlusive material when the basket expands within the bodylumen; an aspiration port providing fluid communication between theaspiration lumen and an interior of the basket; and a distal membranesupported by the distal portion of the basket so as to expand themembrane when the basket is expanded within the body lumen, and aproximal membrane supported by the proximal portion of the basket so asto expand the membrane when the basked is expanded within the bodylumen.
 34. A system for eccentric remodeling of material of a body lumenof a patient, the system comprising: an elongate body having a proximalend and a distal end with an axis therebetween; a radially expandablestructure near the distal end of the catheter body; a plurality ofelectrodes oriented to be urged radially against the material when theexpandable structure expands within the body lumen; a material detectordisposed for circumferential detection of the material; and a powersource electrically coupled to the electrodes, the power sourceenergizing the electrodes so as to eccentrically remodel the detectedmaterial.
 35. A device for occlusive material remodeling in a body lumenof a patient, the device comprising: an elongate body having a proximalend and a distal end with an axial aspiration lumen therebetween; aradially expandable basket near the distal end of the body, the baskethaving a proximal portion and a distal portion with an intermediateportion disposed therebetween; a circumferential electrode arraydistributed circumferentially about the intermediate portion of theradially expandable basket so as to engage adjacent occlusive materialwhen the basket expands within the body lumen; an aspiration portproviding fluid communication between the aspiration lumen and aninterior of the basket; and a distal membrane supported by the distalportion of the basket so as so expand the membrane when the basket isexpanded within the body lumen, and a proximal membrane supported by theproximal portion of the basket so as to expand the membrane when thebasked is expanded within the body lumen.